Lake Tahoe — the largest freshwater alpine lake in North America — is world-famous for its clear blue water, but the lake faces a multitude of threats requiring constant care and vigilance to keep it that way. “We’re more than a bumper sticker,” said Laura Patten, the Natural Resource Director at the League to Save Lake Tahoe, better known as Keep Tahoe Blue. “We really rely on the science to figure out what is happening in the lake.” Patten and other scientists studying Lake Tahoe say climate change and recreation pose the biggest threats to the lake in the 21st century. Longer and hotter periods of heat, more extreme fire seasons, and erratic precipitation patterns in the winter all play a part in Tahoe’s water quality. … It’s important to understand Tahoe’s crystal “blue” water is actually clear. The clear water reflects the blue sky and absorbs red light, making the water appear brilliant hues of blue. The clearer the water — or the better the water’s quality — the bluer the lake.